Microbial Evolution and Epidemiology Laboratory, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, United States.
Microb Pathog. 2011 Dec;51(6):466-70. doi: 10.1016/j.micpath.2011.07.009. Epub 2011 Aug 16.
Variation in disease severity among Escherichia coli O157:H7 infections may result from differential expression of Shiga toxin 2 (Stx2). Eleven strains belonging to four prominent phylogenetic clades, including clade 8 strains representative of the 2006 U.S. spinach outbreak, were examined for stx2 expression by real-time PCR and western blot analysis. Clade 8 strains were shown to overexpress stx2 basally, and following induction with ciprofloxacin when compared to strains from clades 1-3. Differences in stx2 expression generally correlated with Stx2 protein levels. Single-nucleotide polymorphisms identified in regions upstream of stx2AB in clade 8 strains were largely absent in non-clade 8 strains. This study concludes that stx2 overexpression is common to strains from clade 8 associated with hemolytic uremic syndrome, and describes SNPs which may affect stx2 expression and which could be useful in the genetic differentiation of highly-virulent strains.
大肠杆菌 O157:H7 感染的疾病严重程度的差异可能是由于志贺毒素 2（Stx2）的差异表达所致。通过实时 PCR 和 Western blot 分析，对属于四个主要系统发育分支的 11 株菌（包括代表 2006 年美国菠菜暴发的 8 型分支菌株）进行了 Stx2 表达检测。与 1-3 型分支的菌株相比，8 型分支的菌株在基础水平上过度表达 Stx2，并且在用环丙沙星诱导后也是如此。Stx2 表达的差异通常与 Stx2 蛋白水平相关。在 8 型分支菌株 stx2AB 上游区域中鉴定的单核苷酸多态性在非 8 型分支菌株中基本上不存在。本研究得出的结论是，与溶血性尿毒综合征相关的 8 型分支菌株普遍存在 Stx2 过度表达，并描述了可能影响 Stx2 表达的 SNPs，这些 SNPs 可能有助于高度毒力菌株的遗传分化。
